Dave Higdon reviews the evolution of Graphical Broadcast Weather Overlays in the cockpit, offering tips on how to make the most of the services offered by Flight Information System-Broadcasts…
Not long ago, an in-flight pilot's best option for seeing current weather involved using one of three available options: The on-board weather radar, Flight Service Station readings with pilot reports, or the venerable Mk.II EB (i.e. the aviator's own eyes).
Each option offered benefits within its limited scope. But a couple of decades back new options became available, yielding several new opportunities for gaining almost up-to-the-minute weather observations. And since then, the availability of in-flight weather data has expanded to levels that were previously unimaginable…
The first two advances came through on-demand datalink weather, delivered via request/response systems.
The pilot would request an updated report via satellite and either a ground-based system or orbiting satellite broadcast updated that information.
Both came from subscription-based services, and both also had their own limitations. Each required installation of a specialized piece of equipment in the aircraft, thus their popularity centered on the upper end of the GA market.
Pilots at the lower end of the spectrum welcomed the availability of near-live aviation weather graphics delivered via color-screen portable GPS navigators. Indeed, many a corporate pilot opted to augment their business aircraft's on-board weather radar with one of those useful, hand-held navigators.
Weather radar improved with the introduction of digital-Doppler radar systems and color-coded displays, but even then the airborne weather radar still faced constraints.
More satellite- and ground-based sources emerged and avionics OEMs found more ways to accommodate pilots' needs.
Then came the start of a revolution in digital computer technology… namely, the iPad. Cockpit resources changed permanently, and the changes continue today, where graphical weather overlays exist for cockpit avionics as well as for portable devices like the iPad.
Both types offer distinct benefits and advantages. Unfortunately, real-time is still not one of these. Nevertheless, consider the following advances as they relate to graphical weather overlays today.
Take One Tablet for Every Flight…
Today there seem to be as many options for getting graphical-weather images in the cockpit as there are cockpit packages.
Among the earliest iPad buyers were thousands of pilots anxious for access to the numerous aviation apps made available for the tablet almost simultaneously with its release. But the subscription services were always destined to face competition, particularly with the advent of Automatic Dependent Surveillance-Broadcast (ADS-B) In.
For the cost of receiving the hardware (iPad, other tablet or one of many pieces of specialty avionics) any aircraft with the display capability could receive both near-live satellite-based weather and live traffic via the FAA's Flight Information System-Broadcast (FIS-B) and Traffic Information System-Broadcast (TIS-B), with one big difference from the prior subscription-based services: ADS-B In services are free from the FAA after buying a receiver.
The receiver requires some form of display to show the weather (and traffic), and many options exist for this.
The display method most coveted in business aircraft cockpits involves linking the weather receiver to overlay the weather graphics on the cockpit avionics, followed by those systems which work as stand-alone packages independent of the installed electronics.
But even aircraft lacking today's hot new digital displays can enjoy the advantages of datalink weather – if not through the installed avionics, certainly through an iPad or other tablet computer.
The Common Denominators
The FAA's FIS-B resembles many commercial weather services, but with some important differences. First, an aircraft needs an ADS-B In receiver to receive 978 MHz broadcasts, and a display capable of showing the products.
Basically, FIS-B delivers information ranging from text (airport conditions, etc.) to graphic representations of weather radar. Indeed, one of the most-coveted benefits of graphical weather over in-flight radar is its scope.
When using FIS-B an operator can scroll around the map and see weather far beyond the range of airborne weather radar. Figure A provides an inventory of FIS-B products.
FIGURE A: An Inventory of FIS-B Products
The Limitations of Today’s Weather Overlays
Whether from FIS-B or another service supplier, use of weather radar and other information should be utilized with a full understanding of its limitations. FIS-B information (including weather information, NOTAMs and TFR areas), are intended for advisory use only.
The system lacks sufficient resolution and updating capability that is necessary for tactical aerial maneuvering around localized weather phenomena. In extreme scenarios, the oldest weather radar data on the display can be up to 20 minutes older than the display's age indication.
This latency occurs because of the mechanics of how radar and other data come into the system. Doppler weather radar makes six one-minute swings to obtain a full image of weather, from ground-level up into the flight levels. The graphics from those six scans are combined and distributed for broadcast.
By the time the process starts anew as much as 20 minutes may have elapsed from the start of the first sweep of the radar antenna. At its best the images a pilot sees from FIS-B are six minutes old.
Furthermore, pilots cannot claim to have obtained a standard pre-flight weather briefing on the basis of having FIS-B weather information in front of them.
Nevertheless, used regularly FIS-B can deliver life-saving weather information unlike that in any other system, whether shown on a cockpit display or tablet computer. Used wisely graphical weather can make a day's travel more productive than it might otherwise have been.